Oncogenic transformation accompanies dramatic changes in the chemical composition, metabolism, and organization of cell surface glycoconjugates. With the development of the monoclonal antibody approach, it has become apparent that many tumor-associated antigens are carbohydrates that are anomalously expressed not only in specific types of human cancer but also in normal cells and tissues at certain stages of the embryo and fetus and in a few normal unrelated adult cells. For a review, see Hakomori, S., et al., J.Natl.Cancer Inst. 71:231, 1983. Monosialosyl gangliosides such as monosialosyl Le.sup.a, monosialosyl Le.sup.x, monosialosyl dimeric Le.sup.x, and di- or trimeric Le.sup.x, each defined by a specific antibody, are typical of the oncodevelopmental antigens that are expressed in a large variety of human cancers derived from gastrointestinal, pulmobronchial, and mammary gland epithelia. Disialogangliosides GD.sub.3 and GD.sub.2, also defined by specific antibodies, have been identified as melanoma- or neuroblastoma-associated antigens. It would be advantageous to define other tumor-associated disialosyl gangliosides and to establish antibodies reactive specifically thereto.